This invention relates in general to improvements in an earth boring bit assembly, and in particular to a method for assembling and holding drill bit sections in preparation for welding.
One common earth boring bit has three generally conical rotatable cutters. Each cutter is mounted on a bearing pin and rotates about the bearing pin as the bit rotates. The bit is made up of three sections or bit thirds. Each section extends circumferentially 120 degrees and has flat faces on its edges that mate with faces of the two other sections. Each section has a bearing pin that carries one of the cutters.
During manufacturing, each section is first assembled with its cutter. Then the sections are clamped together and welded. A recent technique for welding directs an electron beam against the mating faces of the sections while they are within a vacuum. A continuing problem is in assuring that the gage diameter of the bit is within tolerance, as well as the geometry of the bit body itself.
Prior to electron beam welding, dowel pins were inserted into holes drilled in the 120 degree faces to assure accurate bit geometry. With the advent of electron beam welding of drill bits, various fixtures were proposed, as shown in the following U.S. Patents: 3,907,191, Lichte, Sept. 23, 1975; U.S. Pat. No. 3,987,859, Lichte, Oct. 26, 1976; U.S. Pat. No. 4,045,646, Lichte, Aug. 30, 1977; U.S. Pat. No. 4,098,448, Sciaky et al, July 4, 1978; and U.S. Pat. No. 4,209,124, Baur et al, June 24, 1980.